Build and use the teststale binary on only the host platform.

hack/lib/golang.sh

@@ -114,7 +114,6 @@ kube::golang::test_targets() {
     cmd/linkcheck
     examples/k8petstore/web-server/src
     vendor/github.com/onsi/ginkgo/ginkgo
-    hack/cmd/teststale
     test/e2e/e2e.test
     test/e2e_node/e2e_node.test
   )
@@ -375,6 +374,25 @@ kube::golang::fallback_if_stdlib_not_installable() {
   use_go_build=true
 }
 
+# Builds the toolchain necessary for building kube. This needs to be
+# built only on the host platform.
+# TODO: This builds only the `teststale` binary right now. As we expand
+# this function's capabilities we need to find this a right home.
+# Ideally, not a shell script because testing shell scripts is painful.
+kube::golang::build_kube_toolchain() {
+  local targets=(
+    hack/cmd/teststale
+  )
+
+  local binaries
+  binaries=($(kube::golang::binaries_from_targets "${targets[@]}"))
+
+  kube::log::status "Building the toolchain targets:" "${binaries[@]}"
+  go install "${goflags[@]:+${goflags[@]}}" \
+        -ldflags "${goldflags}" \
+        "${binaries[@]:+${binaries[@]}}"
+}
+
 # Try and replicate the native binary placement of go install without
 # calling go install.
 kube::golang::output_filename_for_binary() {
@@ -444,15 +462,25 @@ kube::golang::build_binaries_for_platform() {
     fi
   fi
 
-  teststale=$(kube::golang::output_filename_for_binary "hack/cmd/teststale" "${platform}")
   for test in "${tests[@]:+${tests[@]}}"; do
     local outfile=$(kube::golang::output_filename_for_binary "${test}" \
       "${platform}")
 
     local testpkg="$(dirname ${test})"
-    if ! ${teststale} -binary "${outfile}" -package "${testpkg}"; then
+
+    # Staleness check always happens on the host machine, so we don't
+    # have to locate the `teststale` binaries for the other platforms.
+    # Since we place the host binaries in `$KUBE_GOPATH/bin`, we can
+    # assume that the binary exists there, if it exists at all.
+    # Otherwise, something has gone wrong with building the `teststale`
+    # binary and we should safely proceed building the test binaries
+    # assuming that they are stale. There is no good reason to error
+    # out.
+    if test -x "${KUBE_GOPATH}/bin/teststale" && ! "${KUBE_GOPATH}/bin/teststale" -binary "${outfile}" -package "${testpkg}"
+    then
       continue
     fi
+
     # `go test -c` below directly builds the binary. It builds the packages,
     # but it never installs them. `go test -i` only installs the dependencies
     # of the test, but not the test package itself. So neither `go test -c`
@@ -564,6 +592,9 @@ kube::golang::build_binaries() {
       fi
     fi
 
+    # First build the toolchain before building any other targets
+    kube::golang::build_kube_toolchain
+
     if [[ "${parallel}" == "true" ]]; then
       kube::log::status "Building go targets for ${platforms[@]} in parallel (output will appear in a burst when complete):" "${targets[@]}"
       local platform